The present invention relates to a spin stabilized projectile unit including a sub-caliber projectile, a propelling cage casing enclosing the projectile, and a propelling base surrounding the projectile and connected to the projectile and the propelling cage casing, wherein the projectile is held in a receptacle of the propelling base by a holding ring.
Projectile units of this type are employed, for example, in the form of cartridge ammunition in automatic weapons and are fired from rifled gun barrels. In modern ammunition of this type, a relatively heavy projectile body is used as the projectile, often composed of heavy metal alloys and held by a sleeve-shaped propelling cage casing usually made of plastic and in a propelling base, frequently made of a light metal and connected with the propelling cage casing.
In practice, it has been found that the propelling cage casing undesirably bursts open prematurely or that damage can occur to the projectile core itself, particularly if the latter is made of a brittle material. This can happen if, during the automatic, cadenced loading along a loading path having a bend, the cartridge hits the end of the gun barrel when entering the cartridge chamber and is delayed. This occurs more frequently with increasingly faster cadence in continuous fire and concomitant developing deceleration forces which are insufficiently absorbed for reliable support of the projectile core.
Various solutions are disclosed in the prior art for projectiles of this type in order to overcome the foregoing problems. For example, German Auslegeschrift [published German Patent Application] No. 2,131,084 discloses a sub-caliber projectile which is seated in a receptacle formed by a propelling base and is surrounded by a propelling cage casing that is connected with the propelling base. The projectile itself is provided with an external groove in its tail section into which a holding ring is inserted so as to force-lockingly fix the projectile in the receptacle in that it engages in an internal groove in the receptacle. The holding ring, in turn, is composed of a coiled tension spring whose interior accommodates a spring steel ring which serves as its core.
In the projectile according German Auslegeschrift No. 2,131,084, the purported favorable effects of the coil spring holding ring during the loading of such ammunition are opposed by considerable drawbacks in the external ballistic behavior of the projectile. Since the coil spring holding ring has a throughgoing bore and the receptacle in the propelling base is provided as a throughgoing ring, the release of the propelling cage from the projectile body after leaving the gun barrel without a pendulum action is not ensured. Additionally, the release occurs only several meters beyond the gun barrel muzzle due to the configuration of the receptacle. Moreover, the rather complicated structure of a steel spring ring as the core and the annular coil spring pulled around it require a relatively large exterior cross section for the entire ring. This necessitates a relatively deep exterior groove in the tail section of the projectile which is unfavorable from a flow technology point of view. Further, because the groove in the tail section of the projectile of German Auslegeschrift No. 2,131,084, is disposed directly behind (when seen in the direction of flight) a cylindrical section of the projectile, the trajectory of the projectile will in almost all cases be adversely affected once the projectile leaves the gun barrel and the propelling cage casing and propelling base have been released.
Additionally, according to the illustration in FIG. 1 of German Auslegeschrift No. 2,131,084, it appears possible that strong deceleration forces during loading will cause the holding ring in its holding groove in the receptacle to be widened radially outwardly to such an extent that the projectile body becomes quasi-freely movable and, as a result of its inertia, destroys the propelling cage casing.
Another drawback of the projectile unit disclosed in German Auslegeschrift No. 2,131,084 is that the required relatively deep exterior groove on the projectile tail results in an undesirable notch effect which has an adverse influence during loading, particularly if brittle materials are employed for the projectile.